Shape lockable apparatus and method for advancing an instrument through unsupported anatomy

ABSTRACT

Apparatus and methods are provided for placing and advancing a diagnostic or therapeutic instrument in a hollow body organ of a tortuous or unsupported anatomy, comprising a handle, an overtube, a distal region having an atraumatic tip. The overtube may be removable from the handle, and have a longitudinal axis disposed at an angle relative to the handle. The overtube may be selectively stiffened to reduce distension of the organ caused by advancement of the diagnostic or therapeutic instrument. The distal region permits passive steering of the overtube caused by deflection of the diagnostic or therapeutic instrument while the atraumatic tip prevents the wall of the organ from becoming caught or pinched during manipulation of the diagnostic or therapeutic instrument.

FIELD OF THE INVENTION

The present invention relates to apparatus and methods for placing andadvancing a diagnostic or therapeutic instrument in a hollow body organof unsupported anatomy, while reducing patient discomfort and risk ofinjury.

BACKGROUND OF THE INVENTION

The use of the colonoscope for examining the interior of the largeintestine or colon is well-known. In general, a physician performing anexamination or treatment of the colon inserts a colonoscope into theanus and then advances the colonoscope into the colon. A completeexamination requires the physician to advance the colonoscope into thecolon, negotiate the sigmoid colon, and left and right colic flexures upto the cecum. Advancement of the colonoscope is generally accomplishedby manipulation of a steerable tip of the colonoscope, which iscontrolled at the proximal end of the device by the physician, inaddition to torquing and pushing the scope forward or pulling itbackward.

Problems regularly occur, however, when negotiating the colonoscopethrough the bends of the colon, such as at the sigmoid and left andright colic flexures. These problems arise because the colon is soft andhas unpredictable fixation points to the viscera of the abdomen, and itis easily distensible. Consequently, after the steerable tip of thecolonoscope is deflected to enter a new region of the colon, theprincipal direction of the force applied by the physician urging theproximal end of the device into the patient's colon is not in thedirection of the steerable tip. Instead, the force is directed along theaxis of the colonoscope towards the preceding bend(s), and causesyielding or displacement of the colon wall.

The loads imposed by the colonoscope on the colon wall can have a myriadof possible effects, ranging from patient discomfort to spasticcramp-like contractions of the colon and even possible perforation ordissection of the colon. Consequently, the colonoscope cannot beadvanced as far as the cecum in up to one-sixth of all cases.

To address some of these difficulties, it is known to employ a guidetube that permits a colonoscope to be advanced through the rectum. Onesuch device is described in U.S. Pat. No. 5,779,624 to Chang. Analternative approach calls for inserting the colonoscope through acurved region, and then mechanically actuating the portion of the devicein the curved region to cause it to straighten, as described in U.S.Pat. No. 4,601,283 to Chikama.

Many patients find the operation of such previously-known devicesunpleasant because the sigmoid portion of the colon is forced into analmost rectilinear shape by the guide tube. Due to the stiffness of theguide tube, careless handling of the guide tube presents a risk ofinjury to the colon.

Other previously-known apparatus and methods use an overtube havingvariable rigidity, so that the overtube may be inserted through curvedanatomy in a flexible state, and then selectively stiffened to resistbending forces generated by passing a colonoscope through the overtube.One example of such a device is described in U.S. Pat. No. 5,337,733 toBauerfiend. The device described in that patent comprises inner andouter walls having opposing ribs spaced apart across an air-filledannulus. The ribs are selectively drawn together to intermesh, and forma rigid structure by evacuating the annulus.

Another previously-known endoscopic device for delivering aneurysm clipswithin a hollow organ or vessel is described in U.S. Pat. No. 5,174,276to Crockard. The device described in that patent includes a conduitformed from a multiplicity of elements that are capable of angulationrelative to one another, and which becomes rigid when subjected to atensile force. The device is described as being particularly useful inneurosurgery, where the variable rigidity of the device is useful forproviding a stable platform for neurosurgical interventions, such asclipping an aneurysm.

While previously-known apparatus and methods provide some suggestionsfor solving the difficulties encountered in advancing diagnostic ortherapeutic instruments through easily distensible body organs, fewdevices are commercially available. Although the precise reasons forthis lack of success are uncertain, previously-known devices appear topose several problems.

For example, the devices described in the Bauerfiend and Crockardpatents appear to pose a risk of capturing or pinching tissue betweenthe endoscope/colonoscope and the distal end of the overtube or conduitwhen the scope is translated. Also, neither device provides any degreeof steerability, and must be advanced along the pre-positioned scope. Inaddition, the bulk of the proximal tensioning system described inCrockard is expected to interfere with manipulation of the endoscope.Other drawbacks of previously-known devices may be related to thecomplexity or cost of such devices or the lack of suitable materials. Inany event, there exists an un-met need for devices to solve thislong-felt problem in the field of endoscopy and colonoscopy.

In view of the foregoing, it would be desirable to provide apparatus andmethods for facilitating placement of diagnostic or therapeuticinstruments within easily distensible hollow body organs, such as theesophagus or colon.

It further would be desirable to provide apparatus and methods thatpermit a diagnostic or therapeutic device to be advanced into a hollowbody organ, and which facilitates passage of the device through tortuousanatomy without requiring straightening of organ passageways alreadytraversed.

It also would be desirable to provide apparatus and methods forfacilitating placement of diagnostic or therapeutic instruments withineasily distensible hollow body organs that include means for reducingthe risk that tissue will become inadvertently pinched between thesheath apparatus and the advancing or withdrawing instrument, or caughtas the diagnostic or therapeutic instrument is maneuvered through thehollow body organ.

It still further would be desirable to provide apparatus and methodsthat provide a low-cost, single use, easily manufacturable guide forinserting a diagnostic or therapeutic instrument in a hollow body organ.

It yet further would be desirable to provide apparatus and methods thatprovide a low-cost, easily manufacturable guide for inserting adiagnostic or therapeutic instrument in a hollow body organ, wherein aportion of the apparatus is disposable after a single use and aremaining portion of the device is re-usable.

Still further, it would be desirable to provide a device having aselectively locking shape for inserting a diagnostic or therapeuticinstrument in a hollow body organ, but which facilitates manipulation ofa proximal end of the diagnostic or therapeutic instrument.

It additionally would be desirable to permit multiple diagnostic ortherapeutic devices to be positioned in a hollow, unsupported organ, sothat at least one of the devices may be withdrawn and repositioned whilethe other devices are retained in place.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide apparatus and methods for facilitating placement of diagnosticor therapeutic instruments within easily distensible or unpredictablysupported hollow body organs, such as the esophagus or colon.

It is a further object of the present invention to provide apparatus andmethods that permit a diagnostic or therapeutic device to be advancedinto a hollow body organ, and which facilitates passage of the devicethrough tortuous anatomy without requiring straightening of organpassageways already traversed.

It also is an object of the present invention to provide apparatus andmethods for facilitating placement of diagnostic or therapeuticinstruments within easily distensible hollow body organs that includemeans for reducing the risk that tissue will become inadvertentlypinched or caught as the diagnostic or therapeutic instrument ismaneuvered through the hollow body organ.

It is a still further object of the present invention to provideapparatus and methods that provide a low-cost, single use, easilymanufacturable guide for inserting a diagnostic or therapeuticinstrument in a hollow body organ.

It is another object of this invention to provide apparatus and methodsthat provide a low-cost, easily manufacturable guide for inserting adiagnostic or therapeutic instrument in a hollow body organ wherein aportion of the apparatus is disposable after a single use and aremaining portion of the device is re-usable.

Still further, it is an object of the present invention to provide adevice having a selectively locking shape for inserting a diagnostic ortherapeutic instrument in a hollow body organ, but which facilitatesmanipulation of a proximal end of the diagnostic or therapeuticinstrument.

It is yet another object of the present invention to permit multiplediagnostic or therapeutic devices to be positioned in a hollow,unsupported organ, so that at least one of the devices may be withdrawnand repositioned while the other devices are retained in place.

These and other objects of the present invention are attained byproviding apparatus comprising a proximal handle, an overtube coupled tothe proximal handle and having a distal region, and an atraumatic tipdisposed on the distal region. The apparatus includes a main lumenextending between the handle, overtube and atraumatic tip, through whicha diagnostic or therapeutic instrument, such as an endoscope orcolonoscope, may be translated.

The handle extends from the patient, e.g., through the mouth or anus,where it can be manipulated by the physician. The handle preferablycomprises means for selectively locking the shape of the overtube. Inthis manner the overtube may be shape locked to assist one or morediagnostic or therapeutic instruments to negotiate the tortuous orunsupported anatomy of a hollow body organ, rather than distending thewall of the organ. The proximal handle may form part of a single use,disposable apparatus, or may be separable from the overtube andreusable. The overtube preferably is angled relative to a working axisof the handle, so that the handle does not interfere with manipulationof the diagnostic or therapeutic instrument inserted through theovertube.

An overtube constructed in accordance with the principles of the presentinvention may comprise a multiplicity of selectively-tensionable nestedelements, a series of interconnected links surrounded by a selectivelyactuable clamping mechanism, a tubular member comprising a multiplicityof helical links formed from a material having variable durometer andsurrounded by a clamping mechanism, or a thermo-responsive polymer oralloy. The overtube may include any of a number of aids for facilitatingpassage of the diagnostic or therapeutic instrument through the mainlumen, including a lubricious liner, rails or rollers.

The atraumatic tip of the present invention preferably is configured toreduce the risk of capturing or pinching tissue between the overtube anda diagnostic or therapeutic instrument that is selectively translatedthrough the overtube. This is preferably accomplished by the atraumatictip applying a radially-outwardly directed load to the wall of thehollow body organ in the vicinity of the distal region where thediagnostic or therapeutic instrument exits the apparatus.

In addition, the distal region of the overtube preferably includes aflexible portion that permits a steerable tip of a diagnostic ortherapeutic device disposed within the distal region to deflect thedistal region of the overtube in a desired direction. This permits theovertube to be readily advanced together with the steerable tip of thediagnostic or therapeutic device.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and the followingdetailed description of the preferred embodiments, in which:

FIG. 1 is a schematic view of a human colon illustrating a commondifficulty encountered in advancing a colonoscope beyond the sigmoidcolon;

FIG. 2 is a side view of illustrative apparatus of the presentinvention;

FIG. 3 is a side-sectional exploded view of nestable elements of a firstembodiment of an overtube suitable for use in the apparatus of FIG. 2;

FIG. 4 is a side-sectional view of a distal region of the apparatus ofFIG. 2 constructed in accordance with principles of the presentinvention;

FIG. 5 is a side-sectional view of an illustrative arrangement of amechanism suitable for use in the handle of the apparatus of FIG. 2;

FIG. 6 is a side-sectional view of the detail of a wire clamping systemsuitable for use in the handle of FIG. 5;

FIGS. 7A-7C are schematic views of a method of using the apparatus ofthe present invention;

FIG. 8 is a schematic view of an alternative step in the method of usingthe apparatus of the present invention;

FIG. 9 is a side view of an alternative embodiment of the apparatus ofthe present invention;

FIGS. 10A and 10B, are a side-section view of an alternative elementsuitable for use in the overtube of FIG. 2 and a roller element suitablefor use with the element of FIG. 10A, respectively;

FIGS. 11A and 11B depict the use of lubricious rails in the overtube ofthe apparatus of FIG. 2 or 9 to facilitate passage of a diagnostic ortherapeutic device through the main lumen;

FIG. 12 is a schematic view of the lumen of the overtube of the presentinvention depicting the use of multiple devices;

FIGS. 13-18 depict side-sectional views of various alternativeembodiments of an atraumatic tip constructed in accordance with thepresent invention;

FIGS. 19A-19C are, respectively, a side-sectional view of an alternativeembodiment of an overtube suitable for use in the present inventionhaving a multiplicity of interconnected links surrounded by a clampingsleeve, and cross-sectional views of portions of the sleeve;

FIG. 20 is a side-sectional view of a further alternative embodiment ofan overtube constructed in accordance with the present invention havinga spiral bladder to actuate the clamping links,

FIG. 21 is a side-sectional view of another alternative embodiment of anovertube of the present invention having thermally-actuable bands;

FIGS. 22A and 22B are side-sectional views of a yet further alternativeembodiment of an overtube of the present invention comprising a seriesof helical links having regions of different durometer; and

FIG. 23 is a side-sectional view of yet another alternative embodimentof an overtube having thermally regulated stiffness.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, problems associated with previously-known apparatusand methods for inserting and advancing a diagnostic or therapeuticinstrument into a hollow body organ having tortuous or unsupportedanatomy, illustratively, patient's colon C, are described. Colon Cincludes sphincter muscle SM disposed between anus A and rectum R.Rectum R is coupled via the rectosigmoid junction RJ to sigmoid colonSC. Sigmoid colon SC joins descending colon DC, which in turn is coupledto transverse colon TC via left colic flexure LCF. Transverse colon TCalso is coupled by right colic flexure RCF to ascending colon AC andcecum CE, which receives waste products from the small intestine.

As illustrated in FIG. 1, colonoscope 10 having steerable distal tip 11is typically inserted through anus A into rectum R, and then steeredthrough rectosigmoid junction RJ into sigmoid colon SC. As depicted inFIG. 1, distal tip 11 of colonoscope 10 is advanced through sigmoidcolon SC and deflected into descending colon DC. Further urging of thecolonoscope by the physician can cause region 12 of the colonoscope tobear against and cause displacement of the rectosigmoid junction RJ, asillustrated by dotted lines 12′ and RJ′ in FIG. 1.

Such distension may result in patient discomfort or spasm, and ifunnoticed, could result in injury to the colon. The potential formovement of colonoscope to cause distension, discomfort or spasm is alsogreat where the colonoscope must negotiate left colic flexure LCF andright colic flexure RCF, and results in a large portion of suchexaminations terminating before the physician can advance distal tip 11to cecum CE.

The present invention provides apparatus and methods for placing adiagnostic or therapeutic instrument through the tortuous orunpredictably supported anatomy of a hollow body organ, such as theesophagus or colon, while reducing the risk of distending or injuringthe organ. Apparatus constructed in accordance with the presentinvention permits an endoscope or colonoscope to be readily advancedinto a patient's tortuous or unsupported anatomy by selectivelyshape-fixing an overtube portion of the apparatus, while also preventingtissue from being captured or pinched between the overtube and scope.

Referring now to FIG. 2, apparatus 20 of the present invention isdescribed. Apparatus 20 comprises handle 21, overtube 22, and distalregion 23 having atraumatic tip 24. Handle 21 includes lumen 25 thatextends from Toughy-Borst valve 26 through overtube 22, distal region 23and atraumatic tip 24. Lumen 25 is configured to facilitate passage of astandard commercially available colonoscope, such as colonoscope 10,therethrough. Toughy-Borst valve 26 may be actuated to releasably lockcolonoscope 10 to apparatus 20 when colonoscope 10 is inserted withinlumen 25. As described hereinafter, overtube 22 is configured so that itcan be selectively transitioned between a flexible state and a rigid,shape-fixed state by actuator 27 disposed on handle 21.

In FIG. 3, illustrative embodiment of overtube 22 comprises amultiplicity of nestable elements 30. For purposes of illustration,nestable elements 30 are shown spaced-apart, but it should be understoodthat elements 30 are disposed so that their adjacent surfaces 31 and 32coact. Each of nestable elements 30 has central bore 33 to accommodatecolonoscope 10, and preferably three or more tension wire bores 35. Whenassembled as shown in FIG. 2, nestable elements 30 are fastened withadjacent surfaces 31 and 32 disposed in a coacting fashion by aplurality of tension wires 36 that extend through tension wire bores 35.

In a preferred embodiment, adjacent surfaces 31 and 32 of each nestableelement 30 are contoured to mate with the next adjacent element, so thatwhen tension wires 33 are relaxed, surfaces 31 and 32 can rotaterelative to one another. Tension wires 36 are fixedly connected to thedistal end of overtube 22 at the distal ends and to a tensioningmechanism disposed within handle 21 at the proximal ends. When actuatedby actuator 27, tension wires 36 impose a load that clamps adjacentsurfaces 31 and 32 of nestable elements 30 together at the currentrelative orientation, thereby fixing the shape of overtube 22.

When the load in tension wires 36 is released, tension wires 36 providesfor relative angular movement between nestable elements 30. This in turnrenders overtube 22 sufficiently flexible to negotiate a tortuous paththrough the colon. When the tensioning mechanism is actuated, however,tension wires 36 are retracted proximally to apply a clamping load tothe nestable elements. This load prevents further relative movementbetween adjacent elements 30, and stiffens overtube 22 so that anydistally directed force applied to colonoscope 10 causes distal tip 11to advance further into the colon, rather than cause overtube 22 to bearagainst the wall of the colon. The shape-fixed overtube absorbs anddistributes vector forces, shielding the colon wall.

Referring now to FIG. 4, an illustrative embodiment of distal region 23and atraumatic tip 24 is described. Distal region 23 comprises flexible,kink-resistant coil 41 encapsulated in flexible layer 42. Layer 42preferably comprises a soft elastomeric and hydrophilic coated material,such as silicon or synthetic rubber, and extends through bores 33 ofnestable elements 30 to form liner 43 for lumen 25. Layer 42 extends tohandle 21 at the proximal end, and at the distal end terminates inenlarged section 44 that forms atraumatic tip 24.

Layer 42 preferably joins with or is integrally formed with flexibleelastomeric cover 45 which encapsulates nestable elements 30 in annularchamber 46. Cover 45 provides a relatively smooth outer surface forovertube 22, and prevents tissue from being captured or pinched duringrelative rotation of adjacent nestable elements 30.

In accordance with one aspect of the present invention, colonoscope 10may be positioned with its distal tip 11 disposed in distal region 23,so that deflection of steerable distal tip 11 imparts an angulardeflection to distal region 23 and atraumatic tip 24. To ensure thatthere is no gross relative motion between colonoscope 10 and apparatus20, Toughy-Borst valve 26 is tightened to engage apparatus 20 to thecolonoscope. In this manner, colonoscope 10 and distal region 23 may besimultaneously advanced through the colon, with the distal tip of thecolonoscope providing a steering capability to apparatus 20. Apparatus20 therefore may be advantageously advanced together with colonoscope 10when overtube 22 is in the flexible state, reducing relative motionbetween apparatus 20 and colonoscope 10 to those instances whereovertube 22 must be shape-locked to prevent distension of the colon.

Still referring to FIG. 4, terminations 47 of tension wires aredescribed. Terminations 47 illustratively comprise balls welded ormolded onto the ends of tension wires 36 that ensure the tension wirescannot be pulled through tension wire bores 35 of the distalmostnestable element 30. This ensures that the nestable elements cannot comeloose when overtube 22 is disposed within a patient.

Alternatively, terminations 47 may comprise knots formed in the ends oftension wires 36, or any suitable fastener that prevents the tensionwires from being drawn through the tension wire bores of the distalmostnestable element. Advantageously, cover 45 provides additional assurancethat all of nestable elements 30 can be safely retrieved from apatient's colon in the unlikely event of a tension wire failure.

Referring now to FIGS. 2 and 5, tension wires 36 within overtube 22,liner 43 and lumen 25 extend from distal region 23, through overtube 22,and to handle 21. Within handle 21, each tension wire 36 passes throughwire lock release 51 fixedly attached to handle 21, and wire lock 52disposed on slide block 53. Each tension wire 36 terminates at wiretension spring 54, which maintains tension wires 36 in light tensioneven when overtube 22 is in the flexible state. The degree of tensionprovided by wire tension springs 54 is not sufficient to clamp adjacentnestable elements 30 together, but on the other hand does not let gapsform between adjacent nestable elements, and helps to manage the tensionwire take up or slack as overtube 22 makes various bends.

Slide block 53 is keyed to slide along rail 55 disposed between limitblocks 56 and 57, and comprises a rigid block having a bore throughwhich rail 55 extends and an additional number of bores as required forthe number of tension wires 36 employed. Rack gear 58 is fixedly coupledto slide block 53. Rack 58 mates with pinion gear 59, which is in turndriven by bi-directional pawl 60 coupled to actuator 27. Pinion gear 59may be selectively engaged by either prong 61 or 62 of bidirectionalpawl 60, depending upon the position of selector switch 63.

If prong 61 is selected to be engaged with pinion gear 59, a squeezingaction applied to actuator 27, illustratively hand grip 64, causes rack53 to move in the D direction in FIG. 5, thereby applying tension totension wires 36. Repeated actuation of hand grip 64 causes slide block53 to move progressively further in direction D, thereby applying anincreasing clamping load on nestable elements 30. Any slack lengths oftension wires 36 extending below slide block 53 are taken up by wiretension springs 54. As discussed in greater detail below with respect toFIG. 6, wire locks 52, which are affixed to slide block 53, engage andretract tension wires 36 concurrently with movement of slide block 53 inthe D direction.

If prong 62 is instead chosen by selector switch 63 to engage piniongear 59, repeated actuation of hand grip 64 causes slide block 53 totranslate in direction U, thereby relaxing the tensile load applied bytension wires 36 to nestable elements 30. Repeated actuation of handgrip 64 causes slide block 53 to advance in direction U until wire lockreleases 51 engage wire locks 52, releasing all tension from tensionwires 36 except that provided by wire tension springs 54. This actionpermits the clamping forces imposed on nestable elements 30 to beprogressively reduced and render overtube 22 progressively moveflexible, until when wire lock releases 51 engage wire locks 52, theovertube is returned to its most flexible state.

Referring to FIG. 6, wire lock 52 and lock release 51 are described ingreater detail. Wire lock 52 includes jaws 65 disposed within collet 66.Collet 66 includes a tapered conical bore 67. Jaws 65 have rampedexterior surfaces 68 and teeth 69, and are biased against the surfaceformed by the tapered conical bore by springs 70. Teeth 69 areconfigured to engage tension wire 36 under the bias force of springs 70.When slide block 53 is moved in direction D (see FIG. 5), jaws 65 engageand grasp tension wire 36 and retract the tension wire in direction D.

To disengage teeth 69 from tension wire 36, e.g., when it is desired toallow overtube 22 to return to a flexible state, slide block 53 isactuated as described previously to move in direction U. Furtheractuation of slide block 53 towards limit block 56 and wire lock release51 causes wire lock release 51 to extend into tapered conical bore 67and push jaws 65 backward against the bias of springs 70. Once tensionwires 36 are freed from jaws 65, overtube 22 returns to its mostflexible state.

Referring to FIGS. 7A-7C, a method of using apparatus 20 is described.Colonoscope 10 and overtube 22 may be inserted into the patient eithersimultaneously or by first backloading the overtube onto thecolonoscope. To perform simultaneous insertion, colonoscope 10 isintroduced into lumen 25 of handle 21 until distal tip 11 of thecolonoscope is disposed in distal region 23. Toughy-Borst valve 26 isactuated to lock apparatus 20 to colonoscope 10. As one unit,colonoscope 10 and overtube 22 are inserted into rectum R of thepatient, and navigated about rectosigmoid junction RJ. As discussedpreviously, steerable distal tip 11 may be used to impart angulardeflection to flexible tip 24 to steer tip 24 about tortuous curves,such as rectosigmoid junction RJ. Once distal tip 11 and tip 24 havebeen negotiated past rectosigmoid junction RJ, the current shape ofovertube 22 is locked in the manner discussed above to provide a rigidchannel through which colonoscope 10 may be further advanced into thecolon without distending rectosigmoid junction RJ. Once distal tip 11 ofcolonoscope 10 is negotiated past sigmoid colon SC, overtube 22 isreleased from its rigid state and advanced along colonoscope 10 until ittoo traverses sigmoid colon SC. Again, the current shape of overtube 22is locked to provide a rigid channel for advancement of colonoscope 10.To negotiate the remainder of the colon, such as left colic flexure LCFand right colic flexure RCF, the preceding steps may be repeated. Inthis manner, colonoscope 10 and overtube 22 may be navigated through thetortuous curves of the colon without distending the colon, and therebycausing discomfort, spasm or injury.

Alternatively, rather than simultaneously inserting both colonoscope 10and overtube 22 into the patient, apparatus 20 first may be backloadedonto the colonoscope. First, overtube 22 is threaded onto colonoscope 10and positioned proximal distal tip 11, as shown in FIG. 8. Colonoscope10 then is inserted into rectum R of the patient and advanced aroundrectosigmoid junction RJ. Overtube 22 is advanced along colonoscope 10into rectum R of the patient, using colonoscope 10 as a guide rail tonegotiate rectosigmoid junction RJ. Once overtube 22 traversesrectosigmoid junction RJ to the position shown in FIG. 7A, the shape ofovertube 22 is locked to provide a rigid channel through whichcolonoscope 10 may be further advanced into the colon. To negotiate theremainder of the colon, the steps discussed in reference to FIGS. 7B-7Cmay be performed.

With respect to FIG. 9, an alternative embodiment of handle 21 isdescribed. Like handle 21 of FIG. 5, handle 71 also embodies aratchet-type tension mechanism, but in this embodiment overtube 22 maybe separated from handle 71, thereby permitting handle 71 to besterilized for repeated use. Handle 71 comprises housing 72 havingactuator 73 that engages teeth 74 disposed along the length of rod 75,which defines working axis W of handle 71. Push knob 76 is affixed tothe proximal end of rod 75 so that when pawl 77 is released, rod 75 maybe pushed in a distal direction. Pawl 77 engages teeth 74 of rod 75 toprevent distally-directed motion of rod 75. Spring 78 biases pawl 77against teeth 74 of rod 75, to provide a one-way ratchet effect whenactuator 73 is squeezed.

As in the embodiment of FIG. 5, tension wires 36 extend through wirelock releases 79, wire locks 80, and are coupled to wire tension springs81. Wire locks 80 are affixed to block 82, which translates withinhousing 72 responsive to movement of rod 75. Wire locks 80 and wire lockreleases 79 operate in the same manner as described with reference toFIG. 6.

In operation, squeezing actuator 73, illustratively a hand grip, causesfork 83 to move rod 75 in a proximal direction so that pawl 77 capturesthe next distalmost tooth 74. This movement also causes wire locks 80 toengage and grasp tension wires 36 and retract the tension wiresproximally. Further actuation of actuator 73 causes overtube 22 tostiffen in the manner previously described. Spring 78 retains pawl 77 incontinuous engagement with teeth 74, thereby preventing rod 75 frommoving in the distal direction.

When it is desired to make overtube 22 more flexible, pawl 77 isreleased and knob 76 pushed in the distal direction so that wire locks80 engage wire lock releases 79. As described above, this releasestension wires 36 from wire locks 80 and permits overtube to assume itsmost flexible state.

In accordance with one aspect of the present invention, overtube 22 ofthe embodiment of FIG. 9 may be replaceably removed from yoke 84 ofhandle 71. In addition tension wires 36 further may comprise connectors85 that permit the tension wires to be disconnected. Such aconfiguration permits the overtube to be removed and discarded after asingle use, while the handle may be sterilized and reused.

Yoke 84 is also configured to position overtube 22 so that longitudinalaxis L of the overtube is angularly displaced from working axis W by apredetermined angle β. This arrangement prevents handle 71 frominterfering with advancement of colonoscope 10 into lumen 25.

In accordance with yet another aspect of the present invention, overtube22 includes atraumatic tip 86 that comprises a soft foam-like material.Atraumatic tip 86 not only facilitates advancement of overtube 22 intraversing tortuous anatomy, but also serves to retain the organ wall asafe distance away from the opening through which the colonoscope isreciprocated by radially expanding the organ wall in the vicinity of thetip, as described hereinbelow with respect to FIG. 14A. Accordingly,atraumatic tip 86 reduces the potential for tissue to be caught orpinched in lumen 25 when the colonoscope is manipulated.

With respect to FIGS. 10A and 10B, an alternative structure is describedto facilitate movement of a colonoscope within lumen 25 of overtube 22.In particular, instead of using inner lining 43 as depicted in FIG. 4,some or all of nestable elements 30 may include roller bearings 87 thatare received in insets 89 formed in nestable elements 30. Bearings 87may be disposed on ring 88 to facilitate assembly of the device.

FIGS. 11A and 11B depict a further alternative embodiment, in whichlubricious flexible rails 90 are disposed within bore 33 of nestableelements 30. Rails 90 span the length of lumen 25, and reduce contactbetween the colonoscope and the interior of the overtube, therebyfacilitating movement of the colonoscope through overtube 22.

In accordance with another aspect of the present invention, the diameterof lumen 25 preferably is configured to facilitate simultaneous passageof more than one diagnostic or therapeutic instrument therethrough. Asshown in FIG. 12, lumen 25 may be dimensioned to permit auxiliarydevices AD, such as for aspiration, biopsy, or additional lighting, tobe advanced alongside colonoscope 10. For example, if lumen 25 has adiameter of 13 mm and colonoscope 10 has an outer diameter of 10 mm,auxiliary device AD, such as a catheter, having a diameter of between 3Fto 9F may be advanced through the remaining space within lumen 25.Advantageously, this permits auxiliary devices AD to be successivelyplaced within the patient's colon to perform additional diagnostic ortherapeutic procedures without the need to remove colonoscope 10 andovertube 22 therefrom.

Referring to FIG. 13, an alternative embodiment of a distal regionsuitable for use in the overtube of the present invention is described.Distal region 100 is similar in construction to distal region 23 of theembodiment of FIG. 4, but has flexible coil 101 embedded in only theproximal portion of elastomeric layer 102. Atraumatic tip 102 at thedistal end of distal region 24 may further enhance the steerability ofthe overtube 22 when the steerable tip of the colonoscope is disposedtherein.

FIGS. 14-18 illustrate additional configurations of atraumatic tipssuitable for causing “tenting” of the wall of the hollow body organ. Asused herein, tenting refers to the tendency of the atraumatic tip to bedeflected radially outward in the vicinity of the tip of the overtube.This reduces the risk that the wall of the organ will become pinched orcaught between the colonoscope and the entry to overtube 22 when thecolonoscope is retracted within the overtube.

FIG. 14A shows atraumatic tip 24 in the form of an inflatabledonut-shaped balloon 110 affixed to distal region 23 of overtube 22.Inflation lumen 111 extends from the handle through overtube 22 toprovide fluid communication between balloon 110 and an inflation source,such as a syringe (not shown). As illustrated in FIG. 14B, when balloon110 is inflated, the wall of the colon radially deflects around balloon110. Thus, when colonoscope 10 is retracted into lumen 25, it is lesslikely that the wall of the colon will be pinched or potentiallydissected between overtube 22 and colonoscope 10.

FIG. 15 depicts a further alternative embodiment of atraumatic tip 24,comprising soft membrane 120 covering shape memory alloy petals 121.Petals 121 preferably comprise loops of shape memory alloy wire, e.g.,nickel titanium alloy, and extend radially outward in the proximaldirection near the distal opening into lumen 25, so that the proximalend of membrane-covered petals causes the “tenting” effect describedhereinabove. The shape memory alloy may be activated to adopt apre-formed shape when exposed to body temperature, and returned to acontracted state by flushing overtube 22 with cold water or air.Alternatively, petals 121 may be mechanically extended or retracted, orself-expanding.

FIG. 16 depicts a further alternative embodiment of atraumatic tip 24.In the embodiment of FIG. 16, petals 130 covered by soft elastomericmembrane 131 extend distally from distal region 23 to form funnel-shapedelement 132. Atraumatic tip 24 provides a similar tenting effect to thatdescribed for the preceding embodiments.

FIGS. 17-18 provide further alternative configurations for atraumatictip 86 of the embodiment of FIG. 9. Tip 140 preferably comprises a foamor soft elastomer, and may be affixed to distal region 23 of overtube 22using a suitable biocompatible adhesive. FIG. 18 depicts an alternativeshape for a foam or soft elastomer bumper 150, which includes aproximally-extending flange 151. Of course, one of ordinary skill in theart will recognize that other configurations may be used in accordancewith the principles of the present invention to form atraumatic tipsthat cause localized tenting of the colon wall, and these atraumatictips may be used with the passively-steerable distal regions of theembodiments of FIGS. 4 and 13.

With respect to FIGS. 19-23, alternative embodiments of overtube 22 aredescribed. Unlike overtube 22 of the above-described embodiments, whichcomprised a multiplicity of nestable elements that are clamped with aplurality of tension wires, the embodiments of FIGS. 19-23 usealternative clamping mechanisms. In particular, the followingembodiments comprise a plurality of links that may be stiffened by theuse of compressive sleeves that compress individual links disposed alongthe length of the overtube.

Referring now to FIGS. 19A-19C, a first alternative embodiment of theovertube of the present invention is described. Overtube 160 comprises amultiplicity of alternating spool links 161 and clamp links 162. Eachspool link 161 and clamp link 162 has a bore disposed therethrough toaccommodate a standard colonoscope. Spool link 161 comprises roundededges 163 disposed on its distal and proximal ends that are contoured topermit limited rotatable engagement with one of two contoured grooves164 disposed within the bore of clamp link 162. Accordingly, clamp link162 comprises a greater outer diameter than spool link 161. Each clamplink 162 also has through-wall split 168 longitudinally disposed topermit a reduction in the diameter of clamp link 162 when the clamp linkis compressed, as discussed hereinafter.

Still referring to FIGS. 19A-19C, a first embodiment of a compressivesleeve comprising inflatable sleeve 165 having first compressiveportions 166 and second compressive portions 167. Sleeve 165 isconfigured so that the inner diameters of second compressive portions167 are smaller than those of first compressive portions 166 when sleeve165 is inflated. Second compressive portions 167 may be disposed toengage clamp links 162. Thus, when inflatable sleeve 165 is inflated byan inflation source (not shown) coupled to the handle, secondcompressive portions 167 compress against clamp links 162 to shape-fixovertube 160. In FIGS. 19B and 19C, cross sectional views of firstcompressive portions 166 and second compressive portions 167,respectively, are shown when sleeve 160 is in its inflated state.

FIG. 20 illustrates an alternative embodiment of a compressive sleevethat also comprises an inflatable bladder. Unlike inflatable bladder 160of FIGS. 19A-19C, spiral bladder 170 has a constant inner diameter.Spiral bladder 170 preferably is helically disposed around the overtube.Accordingly, when bladder 170 is inflated, clamp links 162 arecompressed onto spool links 161 to stiffen the overtube.

FIG. 21 depicts a further embodiment of a compressive sleeve 180,comprising discontinuous hoops 181 made of shape memory alloy (e.g.nickel titanium alloy). Each hoop 181 includes gap 182, which is spannedby spring 183. Each hoop 181 is electrically connected to neighboringhoops 181 via insulated wires 184, so that a serial electrical circuitis established. When hoops 181 are energized, they undergo a phasetransition that causes the hoops to contract into a preformed shape thatis diametrically smaller than the non-energized shape. Since hoops 181may be disposed about clamp links 162, contraction of hoops 181 may beused to apply a clamping load that compresses links 162 onto spool links161 to stiffen the overtube.

Springs 183 contribute to structural integrity when hoops 181 are intheir non-energized state. To energize and thereby contract hoops 181,an electrical current may be run through wires 184. To return hoops 181to their non-contracted state and thereby return the overtube 22 to itsflexible state, hoops 181 may be flushed with cold water or air. Ofcourse one of ordinary skill in the art will recognize that hoops 181also may be individually energized, thus requiring a parallel circuit.

With respect to FIGS. 22A-22B, a still further alternative embodiment ofan overtube suitable for use in the present invention is described. Thisembodiment comprises helical links 190 that are formed from an integralstrip 191 having regions of different durometer, e.g., rigid material192 and soft material 193. When strip 191 is helically wound, helicallinks 190 are formed having rigid portions 194 and soft portions 195.Rigid portions 194 provide structural integrity to the overtube, whilesoft portions 195 provide flexibility.

Helical links 190 are disposed within compressive sleeve 196, whichincludes first compressive portions 197 and second compressive portions198. Compressive sleeve 196 is identical in structure and operation tothat described in FIGS. 19A-19C, except that second compressive portions198 are aligned with, and apply a clamping force to, rigid portions 194of helical links 190. It will of course be understood that an overtubein accordance with the principles of the present invention couldalternatively be formed using helical links 190 and either of theclamping systems described with respect to FIGS. 20 and 21.

With respect to FIG. 23, a still further embodiment of an overtubesuitable for use in the apparatus of the present invention is described.Overtube 200 comprises a heat-softenable polymer layer 201, (e.g.,Carbothane®, a proprietary urethane-based polymer available fromThermedics Polymer Products, Woburn, Mass.), having wire 202 embeddedwithin it. Wire 202 is coupled at the handle to an energy source, sothat by passing an electric current through wire 202, sufficientresistive heating occurs to soften the polymer layer 201, rendering itsufficiently flexible to negotiate tortuous or unsupported anatomy. Whenelectrical energy is not supplied to wire 202, no resistive heating ofthe wire or the polymer layer occurs, and the overtube instead cools andstiffens. Wire 202 serves the dual purpose of providing kink resistanceand electric heating.

Still referring to FIG. 23, yet another alternative embodiment of anovertube suitable for use in the present invention comprises a softelastomeric polymer layer 201 having a shape memory alloy wire 202embedded within layer 201. In this embodiment, the shape memory alloy isselected to have a martensite transition temperature above bodytemperature. When wire 202 is heated to a temperature above bodytemperature, such as by passing an electric current through it, the wiretransitions into the austenitic phase, and becomes stiffer, therebyshape locking the overtube. When application of the electric currentceases, wire 202 cools back into the martensitic phase, and renders theovertube flexible.

While preferred illustrative embodiments of the invention are describedabove, it will be apparent to one skilled in the art that variouschanges and modifications may be made therein without departing from theinvention. The appended claims are intended to cover all such changesand modifications that fall within the true spirit and scope of theinvention.

What is claimed is:
 1. Apparatus for advancing a first diagnostic ortherapeutic instrument into a hollow body organ of unsupported anatomy,the apparatus comprising: a reusable handle; an overtube having aremovable component coupled to the handle, the overtube having anelongated portion, a distal opening, a proximal opening and a lumenextending therebetween to permit passage of a first diagnostic ortherapeutic instrument; and an elastomeric member defining an annularchamber configured to accept the overtube, the elastomeric member havinga first portion that forms a liner for the lumen of the overtube, asecond portion that forms an exterior cover for the overtube, and anatraumatic tip disposed adjacent to the distal opening.
 2. The apparatusof claim 1 wherein the overtube includes means for locking the overtubein a bent configuration.
 3. The apparatus of claim 2 wherein the meansfor locking the overtube in a bent configuration comprises: a pluralityof nestable elements; a plurality of tension wires that thread thenested elements together; and a tensioning mechanism that may bereleasably coupled to the plurality of tension wires and to selectivelyapply a clamping load to the plurality of nestable elements.
 4. Theapparatus of claim 3 wherein the tensioning mechanism is a ratchet-typetensioning mechanism.
 5. The apparatus of claim 2 wherein the means forlocking the overtube in a bent configuration comprises: a plurality oflinks, each link having a bore that defines the lumen of the overtube;and means for applying a clamping load to the plurality of links.
 6. Theapparatus of claim 5 wherein the plurality of links comprise: aplurality of spool links, each one of the spool links having roundeddistal and proximal ends; and a plurality of clamp links, each one ofthe clamp links interposed between adjacent ones of the plurality ofspool links, each one of the clamp links having an interior surfacehaving grooves adapted to engage a distal end of a first adjacent spoollink and a proximal end of a second adjacent spool link.
 7. Theapparatus of claim 5 wherein the plurality of links comprise amultiplicity of helical links formed from a material having variabledurometer, each helical link having a rigid portion and a soft portion.8. The apparatus of claim 5 wherein the means for applying a clampingload comprises an elongate inflatable sleeve disposed to surround theplurality of links.
 9. The apparatus of claim 8 wherein the elongateinflatable sleeve comprises a plurality of interconnected annularbladders.
 10. The apparatus of claim 8 wherein the elongate inflatablesleeve has a helical shape.
 11. The apparatus of claim 5 wherein themeans for applying a clamping load comprises a plurality ofdiscontinuous, circular hoops made of a shape memory alloy; and aplurality of insulated wires that connect the plurality of hoops to anelectrical source.
 12. The apparatus of claim 2 wherein the means forlocking the overtube in a bent configuration comprises a heat-softenablelayer having an embedded wire, wherein an electric current passingthrough the embedded wire softens the heat-softenable layer.
 13. Theapparatus of claim 2 wherein the means for locking the overtube in abent configuration comprises a soft layer having an embedded shapememory alloy wire.
 14. The apparatus of claim 1 wherein the atraumatictip comprises an inflatable donut-shaped balloon.
 15. The apparatus ofclaim 1 wherein the atraumatic tip comprises a wire petal having anelastomeric covering.
 16. The apparatus of claim 1 wherein theatraumatic tip comprises a foam or soft elastomer bumper.
 17. Theapparatus of claim 1 wherein the overtube includes means forfacilitating passage of the first diagnostic or therapeutic instrumentthrough the lumen of the overtube.
 18. The apparatus of claim 1, whereinthe reusable handle has a working axis, and the lumen has a longitudinalaxis, wherein the longitudinal axis is angled relative to the workingaxis.
 19. The apparatus of claim 1, wherein the lumen is dimensioned topermit passage of a second diagnostic or therapeutic instrumentalongside the first diagnostic or therapeutic instrument.
 20. A methodfor advancing a first diagnostic or therapeutic instrument having asteerable distal tip into an unsupported, hollow body organ, the methodcomprising: providing an apparatus having a reusable handle and anovertube having a releasable component coupled to the handle, theovertube comprising an elongated portion having a distal opening, aproximal opening and a lumen extending therebetween to permit passage ofthe first diagnostic or therapeutic instrument, and an elastomericmember defining an annular chamber configured to accept the overtube,the elastomeric member having a first portion, a second portion, and anatraumatic tip; applying the elastomeric member to the overtube so thatthe first portion forms a liner for the lumen of the overtube and thesecond portion forms an exterior cover of the overtube; and insertingthe apparatus and the first diagnostic or therapeutic instrument intothe unsupported, hollow body organ; uncoupling the the releasablecomponent from the reusable handle after the apparatus and the firstdiagnostic or therapeutic instrument has been removed from theunsupported, hollow body organ.
 21. The method of claim 20 whereinproviding an apparatus comprises providing an apparatus wherein thereusable handle has a working axis, the method further comprisingadvancing the first diagnostic or therapeutic instrument through thelumen at an angle relative to the working axis of the handle.
 22. Themethod of claim 20 wherein providing an apparatus comprises providing anapparatus wherein the atraumatic tip comprises an inflatable donutshaped balloon, the method further comprising deflecting theunsupported, hollow body organ by inflating the inflatable donut shapedballoon.
 23. The method of claim 20 wherein providing an apparatuscomprises providing an apparatus wherein the atraumatic tip comprises awire petal having an elastomeric covering, the method further comprisingdeflecting the unsupported, hollow body organ by extending the wirepetal in a radially-outwardly direction.
 24. The method of claim 20wherein providing an apparatus comprises providing an apparatus whereinthe atraumatic tip comprises a foam or soft elastomer bumper, the methodfurther comprising deflecting the unsupported, hollow body organ bycontacting the foam or soft elastomer bumper against the unsupported,hollow body organ.
 25. The method of claim 20 further comprising:locking the overtube in a bent configuration; and advancing the firstdiagnostic or therapeutic instrument through the lumen of the overtubein the bent configuration.
 26. The method of claim 25 wherein providingan apparatus comprises providing an apparatus wherein the overtubecomprises a plurality of nestable elements, and a tensioning mechanismthat selectively applies a clamping load to the plurality of nestableelements, and locking the overtube in a bent configuration comprisesactuating the tensioning mechanism.
 27. The method of claim 25 whereinproviding an apparatus comprises providing an apparatus wherein theovertube comprises a plurality of links, each link having a bore thatdefines the lumen of the overtube and locking the overtube in a bentconfiguration comprises applying a clamping load to the plurality oflinks.
 28. The method of claim 27 wherein the overtube further comprisesan elongate inflatable sleeve disposed to surround the plurality oflinks, and applying a clamping load to the plurality of links comprisesinflating the elongate inflatable sleeve.
 29. The method of claim 27wherein the overtube further comprises a plurality of discontinuous,circular hoops made of a shape memory alloy, and applying a clampingload to the plurality of links comprises inducing the plurality ofdiscontinuous, circular hoops to undergo a phase transition.
 30. Themethod of claim 25 wherein providing an apparatus comprises providing anapparatus wherein the overtube comprises a heat-softenable layer havingan embedded wire, and locking the overtube in a bent configurationcomprises terminating a supply of electrical energy to the embeddedwire.
 31. The method of claim 25 wherein providing an apparatuscomprises providing an apparatus wherein the overtube comprises a softlayer having an embedded shape memory alloy wire, and locking theovertube in a bent configuration comprises heating the embedded shapememory alloy wire.
 32. The method of claim 20, wherein providing anapparatus comprises providing an apparatus wherein the lumen isdimensioned to permit passage of a second diagnostic or therapeuticinstrument alongside the first diagnostic or therapeutic instrument, themethod further comprising advancing the second diagnostic or therapeuticinstrument alongside the first diagnostic or therapeutic instrument.